Optical methods of three-dimensional profilometry have been of growing interest in both industrial and scientific applications. These techniques provide absolutely non-destructive measurement due to their non-contact nature and maintain their high precision in a large field of view. Most of these techniques however, are based on interferometry which happens to be considerably sensitive to environmental noises such as turbulence and vibration. We have used the phenomena of Fresnel diffraction from phase-steps instead of interferometry to maintain a higher precision and reduce sensitivity to environmental noises. This phenomena has been recently introduced as a method for precise measurement of wavelength, thickness and refractive index. A 2D array of reflective disks are placed above the test surface to provide the required phase-steps. In this paper, theoretical principles of Fresnel diffraction from phase-steps are discussed and the experimental results of testing an optical flat surface are presented. A flat mirror surface has been tested as an optical test surface and is been profiled. The results show that the method is precise and is not sensitive to environmental noises such as vibration and turbulence. Furthermore, the method seems to be a powerful means for testing of curved surfaces, too.
In this paper we use digital projection moiré (DPM) method to analyze the non-linear behavior of sandwich beams with compliant foam core. These cores are highly flexible with respect to the face sheets and their behavior is associated with localized effects in the form of localized displacements and stresses, which in turn influence the overall behavior of sandwich beams. In this study we compare the results of three point bending with Finite Element Analysis (FEA) results that are obtained from the ABAQUS finite element code. We have shown that DPM experimental results are in good agreement with FEA simulations. It is suggested that the presented method can be used as a simple, advantageous and user friendly whole-field testing technique for many applications in evaluation of composite materials and sandwich structures.